Wearing headphones while walking can be a risky business, new research from the University of Maryland suggests.

In a study published Tuesday in the journal Injury Prevention, researchers looked at reported pedestrian-vehicle collisions in which the pedestrian was wearing headphones -- either the traditional cover-the-whole-ear variety or ear buds that fit into the ear itself. They found 116 reports of death or injury that occurred under such circumstances between 2004 and 2011. While only 16 took place in 2004, nearly three times that number (47) took place in 2011. Overall, 81 of the collisions resulted in the headphone-wearer’s death.

Nearly 70 percent of the victims were male, and about two-thirds were under age 30. Most of the accidents (59 percent) took place in areas classified as urban; only 12 percent took place in areas considered rural. In 34 of the 116 cases, reports made a point of mentioning that horns or sirens had been sounded before the victim was struck.

I was surprised to learn that more than half (55 percent) of the accidents involved people’s being struck by trains. That statistic may not have surprised the research team, though, as they note they were spurred to undertake the study in part by much-publicized incident in which a man wearing headphones was struck and killed by an Amtrak train in Baltimore in February 2011.

The authors suggest that wearing headphones might contribute to increased risk of being struck by a vehicle in two ways. “Inattentional blindness,” the report explains, is a form of distraction associated with the use of electronic devices; people using such devices divide their attention between listening to whatever sound the device is producing, manipulating the device’s controls, and whatever tasks they really should be paying attention to (such as, well, walking). The other means by which headphones raise risk is by causing a form of sensory deprivation called “environmental isolation.” That’s a fancy way of saying the earphones block out external sounds -- such as horns and sirens.

The authors note that their study design doesn’t allow them to establish a cause and effect relationship between headphone use and pedestrian’s being struck by vehicles. They also point out that other factors such as suicidal intentions, substance abuse or mental illness might have been in play in some of the cases reported.